Originally Posted by rodin

If you had studied the thread properly you would have seen that expansion then contraction was my proposal. Also where the mass came from and went. The exact mechanism still to be determined but essentially it is a nuclear reaction expanding collapsed/condensed matter into atoms thereby expanding volume but not mass. Later hydrogen and/or helium produced that did not compound with the mantle or atmospheric oxygen would evaporate into space and quickly from an enlarged planet with lower gravity. Hydrogen is still bubbling up and can still escape Earth's gravity into space